Treating hydrocarbon distillates



Patented Dec. 22, 1.942

2,305,142 mm'rma nrnnocaaaon msmm'ms William King Simpson and Charles G. Dryer, Chicago, Ill., assignors to Universal Oil Products Company, Chicago, 111., a corporation of Delaware No Drawing. Application March 25, 1939,

Serial No. 284,130

5 Claims. (Cl. 196-39) This invention is particularly concerned with the treatment of motor fuel obtained by cracking of heavy oils from petroleum, or from the prifiry distillation of shale oil, coal tar, and the Many treating methods have been proposed for the refining of hydrocarbon distillates, and these have been used, to "a greater or lesser extent throughout the development of the petroleum industry. Among the widely used methods, particularly for gasoline refining, is treatment with sulfuric acid which results in improved color, reduced sulfur content, and improved storage stability, particularly from the standpoint of gum formation.

Another method makes use of the refining effects of adsorbent materials including natural earths of the clay type, such as fullers earth, which may or may not be activated by chemical treatment. The refining action of the so-called clay treating process may be carried outwith the gasoline in either the liquid or the vapor phase, depending on the temperature and pressure conditions. The method is widely used, particularly in connection with the more readily treated distillates having low sulfur contents. It is with improvements in this process that the present invention is concerned.

In one specific embodiment our invention com prises treating cracked motor fuel with an acidic substance such as a dilute acid, separating said motor fuel, and then contacting it with an ad sorbent refining agent such as fuliers earth under conditions adequate to effect improvement in color and gum content.

It has been found that certain cracked distillates resist treatment with adsorbent refining agents, so that low yields are obtained and the treating method is not an economical procedure. Formerly such distillates were largely treated with sulfuric acid, but since the strict sulfur specifications of the past no longer apply, many of these distillates are not given the more severe acid treatment. However, refining of these distillates with strong acids has been continued by many refiners because no other economical method has been available and the distillates require treatment in some form before they can be marketed. We have discovered that the yields per ton of reagent and the quality of the product resulting from the clay treatment of cracked gasolines, and especially the refractory gasolines described above, can be materially improved by treating them prior to fuller's earth treatment with relatively small quantities of dilute acids,

ing to our method cracked gasolines are con-' tacted with a dilute solution of mineral acid of from l-20% concentration prior to clay treating. Although the concentrations given are those preferred, in certain instances more concentrated acid may be used. Acid strength will depend upon the gasoline being treated and the acid being used. For example; concentrations up to 20 or even of sulfuric acid may sometimes be employed satisfactorily. On the other hand, if hydrochloric acid is used we prefer concentrations of 10% or less in order to avoid undesirable chlorination of the gasoline. Concentrations of phosphoric acid similar to those employed with sulfuric acid are satisfactory. The contacting of the acid and gasoline may be carried out in any suitable apparatus, the most satisfactory of which are of the countercurrent type in order to obtain maximum acid utilization. After treatment with the acid and separation of the aqueous layer, the gasoline is normally washed with water to remove traces of suspended acid, and neutralized In certain instances this step may be dispensed with, although the caustic treatment sometimes contributes materially to the beneficial eifect obtained. The neutralized distillate is heated to the desired treating temperature, normally within the range of approximately 250-600 F., and then passed into contact with an adsorbent treating reagent such as fullers earth, which is used for the main refining operation. This operation may be carried out in the so-called liquid phase operation at superatmospheric pressure so that the gasoline is maintained in substantially liquid phase, the pressures normally being in the range of approximately -1000 pounds per square inch or higher. In the so-called vapor phase operation the pressure may be only such as to permit the ready passage of the vapors through the treating reagent, rarely exceeding a maximum of 50-100 pounds per/square inch. The treatment with the adsorbent is followed by a fractionation step to remove higher-boiling bottoms which are present in the treated distillate as a result of the polymerizing elfect of the ad-, sorbent on the unsaturated hydrocarbons. The

treatment with an adsorbent is well known and may be carried out in any suitable apparatus. The improvement which we have devised consists in contacting with dilute acid and then clay treating distillates. This should not be confused with methods which have been previously proposed whereby I motor fuels, are treated with strong acids, that is, for example, sulfuric acid of greater than 50% concentration or concentrated hydrochloric acid following vapor or liquid phase treatment with clay or other natural earths or minerals. The dilute acid treatment which We employ has but little refining effect in itself, so that the gasoline after this treatment even when followed by redistillatio'n with fire and steam, is not of a suitable salable quality. In

our process upon the yields which may be realized from clay treatment cannot be attributed to the removal of the usual type of undesirable, unstable compounds'present in gasoline, since the was obtained with the natural fullers earth used. The storage stability and the gum content was satisfactory when 0.005% of a. commercial gum inhibitor was added. However, the life of the clay was too low to be considered economical.

The raw gasoline was then treated according to the process of the invention with 5% by volume of sulfuric acid, followed by neutralization of the treated material which was other words, the beneficial effect obtained by l0 then passed into contact ,with fullers earth as previously described. The yield in this case was 2500 barrels per tons of clay, the gasoline having J a 25 color, an oxygen bomb induction period of strength of the acid employed is such that these particular compounds are in general unaffected. To confirm this we have found that the boiling range of the gasoline is unchanged by the dilute acid treatment, and that none of the usual'decomposition, polymerization, and desulfurization occurs.

We have also employed with success, acid salts and other acidic substances which in aqueous: solution yield solutions of less than 7.0 pH, and the term acidic substance as used herein is understood to cover such compounds. Typical of these are sodium, potassium, and ammonium acid sulfates; and ferric chloride, zinc chloride, aluminum chloride, etc., which are used in dilute solutions preferably of less than 20% concentration which we have found to be suitable and of such dilution that substantially no polymerizing or sludge-forming effect is produced.

The adsorbents which have been found useful in the second step include the natural earths of the clay type, particularly fullers earth, fioridin, and similar earths. Other adsorbents include bauxite, activated alumina, activated carbon, silica gel, green sand, etc. Another type of adsorbent of particular value is the activated one will be found more eflective, while in other cases another reagent will be more suitable.

The following examples are given to illustrate our invention and should be construed as demonstrating its practicability and proving its usefulness but should in no way be interpreted as limiting it to the exact conditions given therein.

Example I A gasoline obtained by cracking a California crude oil was found to possess a. foul odor which could not entirely be attributed to the mercaptan content. It was of orange color when fresh'and rapidly changed upon standing to a muddy red and eventually a sediment deposited. This gasolne was treated according .to the conventional 150 minutes and 25 mg. of copper dish gum per 100 cc. The induction period was raised to 325 minutes and the gum lowered to 5 mg. by addi-' tion of 0.0025% of a commercial inhibitor. By accepting a color of 21 Saybolt, the yield obtained was increasedto 3000 barrels per ton.

Example If The gasoline of Example I was refined without the preliminary wash at similar conditions of operation using an acid activated fullers earth as the treating material. When treating the gasoline as produced a yield of 1600 barrels per ton of 25 color gasoline was obtained. When processing the gasoline after treatment with 5% of 10% sulfuric acid, the yield of 25 color gasoline was increased to 3000 barrels per ton. This gasoline was readily stabilized by the addition of 0.0025% of a commercial gum inhibitor. The inhibited gasoline had an oxygen bomb induction period of 310 minutes and a copper dish gum content of 5mg.

Example III The gasoline used in Example I was treated with 2 pounds of 5% sulfuric acid per barrel of oil, neutralized and clay treated at 450 F. and 200 pounds per square inch pressure using the activated earth referred to in Example II. The properties of the gasoline after treating 4000 barrels per ton of earth were, color +23, and copper dish gum 10 mg. per 100 cc. Only 1800 barrels per ton of 23 color gasoline could be obtained without pretreatment.

We claim as our invention:

1. In the treatment of gasoline with solid adsorbent refining agents, the method of prolonging the life of the adsorbent which comprises initially treating the gasoline with a relatively small amount of a dilute aqueous solution of a mineral acid in concentration of about 1 to 20%,

5 the quantity of said solution being insufficient to vapor-phase clay method using a typical fullers earth. The run was made in order to ascertain whether or not the usual clay treatment was applicable to the distillate. The particular mar- .ket requirements of the refiner concerned 'were color gasoline, a yield of only 900 barrels per ton eifect any substantial refining of the asoline, and thereafter refining the gasoline by contacting the same with the solid adsorbent at a temperature in the approximate range of 250-600" F.

2. In the treatment of gasoline with solid adsorbent refining agents, the method of prolonging the life of' the adsorbent which comprises initially treating the gasoline with a relatively small amount of a dilute solution of sulfuric acid in concentration of about 1 to 30%, the quantity and concentration of said solution being insufficient to effect any substantial refining of the gasoline, and thereafter refining the gasoline by contacting the same with the solid adsorbent at a temperature in the approximate range of 250-600 F.

3. In the treatment of gasoline with solid adsorbent refining agents, the method of prolonging the life of the adsorbent which comprises initially treating the asoline with an aqueous solution of a mineral acid, said solution corresponding in amount and strength to approximately 5% of a 140% sulfuric acid solution, whereby to condition the gasoline for the adsorbent treatment without any substantial refining thereof, and thereafter contacting the gasoline with the solid adsorbent.

{In the treatment of gasoline with solid ad-. sorbent refining agents, the method of prolonging the life of the adsorbent which comprises initially treating the gasoline with approximately 5% of a 1-20% sulfuric acid solutio whereby to condition the gasoline for the adsor 't treat- 10 adsorbent.

ment without any substantial refining thereof, and thereafter contacting the gasoline with the solid adsorbent. e

5. In the treatment of gasoline with solid adsorbent refining agents, the method of prolonging the life of the adsorbent which comprises initially treating the gasoline with about 5% or an approximately 10% sulfuric acid solution, and thereafter contacting the gasoline with the solid WIILIAM KING SIMPSON.

CHARLESG. DRYER. 

